Many common surfactants used in cleaning compositions are difficult to handle in a concentrated form. In particular, it is known that some anionic surfactants such as alkyl sulfates (AS) and alkyl ethoxy sulfates (AES) exhibit a prohibitively viscous hexagonal phase for concentrations in the range of roughly 30% to 60% by weight active surfactant, while exhibiting a thick but flowable lamellar phase at somewhat higher concentrations.
To save on transportation and storage costs, it is desired to handle these anionic surfactants in a concentrated form. However, in order to dilute the lamellar phase into an isotropic phase as typically in the final liquid cleaning composition, care must be taken to mitigate the hexagonal phase or at least shorten the time of transitioning through the hexagonal phase. Otherwise, it can take hours to days to dilute this highly viscous hexagonal phase further due to the slow mixing dynamics, rendering dilution of the lamellar phase via simple mixing as impractical on an industrial scale.
To mitigate the hexagonal phase, one approach in the prior art is to add a second material, usually a hydrotrope, to the lamellar surfactant. Where the addition of another material to mitigate the hexagonal phase is not desirable, the common solution is to dilute the lamellar phase very carefully into water. However, both of the approaches require separation of the dilution operation and may even face a subsequent issue of removing the undesired material or excessive amount of water from the final composition.
Moreover, some ingredients in the liquid cleaning composition are known to act as a gel breaker (in addition to their principal role in the cleaning composition), and the prior art discloses utilizing these ingredients to dilute the concentrated lamellar surfactants. This approach indeed eliminates the need for a separate dilution operation as well as the need for a subsequent step of removing undesired material or excessive amount of water. However, this approach is typically conducted in an in-line process and the gel breaker is diluted by other ingredients in the cleaning composition, thereby diminishing an ingredient's impact as a gel breaker. Also, this approach requires a deep understanding of the impact of formulation ingredients on the phase behavior and a precise control of ratios of the ingredients in the formulation, both of which are difficult to achieve, particularly on an industrial scale. Furthermore, this approach is not flexible for a range of formulations given the complexity posed by varying ingredients and concentrations.
Therefore, there is a need for a process of making a liquid cleaning composition that mitigates the hexagonal phase whilst allowing for maximum flexibility in formulating various ingredients in the composition.
It is an advantage of the present invention to provide a process of making a liquid cleaning composition that allows for expanding production capacity.
It is another advantage of the present invention to provide an efficient process of making a liquid cleaning composition without requiring a precise control of ratios of ingredients or relatively high energy input.
It is yet another advantage of the present invention to provide a process of making a liquid cleaning composition, which increases the processible surfactant concentration range and which eliminates the need for a separate dilution operation as to concentrated surfactants as well as the need for a subsequent step of removing undesired material or excessive amount of water.